Practical preparation for coding tests and interviews, directly taught by interviewers from Naver, Kakao, Line, Coupang, and Baemin.

This course provides a step-by-step learning path, ranging from the fundamental usage of MySQL to advanced techniques required in real-world production environments. It covers a wide range of topics, including data modeling techniques based on various case studies and practical data, evaluating the effectiveness of Foreign Key designs, analyzing Google Calendar schema DDL, and modern DDL design principles. Through this course, you will gain an in-depth understanding of how to utilize MySQL as a core system component rather than just a simple database.

Develop a scalable order processing system with real-time event streaming capabilities using Spring Boot 3.x + Kotlin to build a Kafka cluster, leveraging PostgreSQL CDC, Debezium Connect, and Apache Avro schema.

Most developers are still stuck on Batch and CronJobs when it comes to data processing. However, in real-world production environments, data is generated continuously, and failing to process that flow immediately leads to latency, bottlenecks, and consistency issues. Having personally dealt with real-time recommendations, state synchronization, and event delay problems in high-traffic environments, I’ve often asked myself, "Is batch processing really the right approach for this?" This course begins with that very question. It explores how to use Apache Flink to perform computations the moment data flows, manage state securely, and produce accurate results based on Event Time—all from a practical perspective. Beyond simple theoretical explanations, you will experience how real-time stream processing systems are designed and operated through actual source code and architectures. For those who found real-time processing vague or were curious about the world beyond messaging, this course will provide a clear sense of direction.

I'll show you how to use Redis effectively, along with its precautions and best practices, using real-world examples from actual work environments and well-known case histories.

Learn SAGA transaction management techniques for maintaining data consistency in distributed environments through hands-on practice. Build 3 microservices using Spring Boot and Docker, and implement both Orchestration and Choreography patterns with Kafka and MySQL. Through this course, you can master core concepts that are immediately applicable in real-world scenarios, including distributed transaction operation principles, compensating transaction design, and failure recovery handling.

Learn how to design and process large-scale data architecture that handles hundreds of billions of data records using only pure SQL and MySQL's core features, together with a Toss developer who handles hundreds of billions of financial traffic transactions and a developer who started as a non-major and is now developing platforms in Pangyo.

How do you handle exploding traffic? Learn how to build resilient and flexibly scalable architectures through practical design patterns based on EDA (Event-Driven Architecture) using Kafka, Spring, CDC, and Temporal. Explained clearly and simply with real-world experience from a Kakao developer, making it accessible even for non-majors. A hands-on, practical course covering real-time data flow, event processing, and microservice integration all at once!

Learn the process of building data pipelines using Apache Airflow from basics to practical application. Understand Airflow's core concepts and architecture, and master advanced design patterns frequently used in practice such as dynamic DAGs, parallel processing, distributed processing, and Custom Operators through hands-on exercises. Set up a practice environment with Python and Docker, and develop practical skills to design and operate real workflows.

This course covers how to set up multi-module projects from scratch using Kotlin and Spring Boot. It proceeds with a hands-on approach, covering everything from the basic concepts of modularization to Gradle configuration, managing dependencies between modules, and actual application development. If you are a beginner or intermediate developer looking to learn the fundamentals and practical application of multi-modules, please refer to this course.

Learn the process of building essential Observability in a Microservices Architecture (MSA) environment from basics to practical application. Master standardized data collection using OpenTelemetry, trace storage and search through Grafana Tempo, and visualization using TraceQL through step-by-step hands-on practice. You can learn how to track service flows through distributed tracing, identify bottlenecks, and analyze the root causes of failures.

I am covering the know-how on how I studied and got a job, starting as a non-major.

In this course, rather than directly covering theory, you will learn how to effectively use Redis in code through hands-on practice.

Using Spring Boot 3.x + Kotlin, we build a 3-instance cluster, and utilizing Redis Pub/Sub distributed messaging and an Nginx load balancer, develop a scalable WebSocket real-time chat server capable of handling large-scale traffic.

This course explores microservice architecture and distributed environments not as a simple list of technologies, but from a 'design perspective' required in actual work and interviews. Starting from the differences between monolithic and MSA, it progressively covers incremental migration strategies, modular monoliths, clean architecture and hexagonal architecture, clearly explaining why each choice is necessary and the trade-offs involved. Through hands-on practice, you can directly verify the intent of the structure and learn about core issues inevitably encountered in distributed environments—such as data consistency, transactions, inter-service communication, and failure handling—through realistic scenarios. Based on actual questions and perspectives from Kakao interviewers, this course aims to go beyond simple knowledge acquisition and elevate your way of thinking about distributed systems to the next level.

You can learn about JWT and ws communication using Spring Boot, and how to handle high TPS.

When you're doing backend development, at some point you face this dilemma. As services grow and traffic increases, there comes a moment when simple REST communication and CRUD structures feel limiting. I experienced the same problem in real-world work and went through many trials and errors between performance and structural complexity. The solution I chose in that process was NATS. Its simple configuration based on a single binary, ultra-low latency performance in microseconds, and the fact that it provides just the right amount of essential features for real work—from Pub/Sub to Queue Groups and JetStream—made it a very practical choice in actual service environments. This course is not about listing NATS features. Based on the problems I faced in real work, I explain with code and flow diagrams which situations led me to choose NATS, why, and how I designed the architecture. This is a course designed to help everyone—from those new to messaging systems, to backend developers preparing for jobs, to senior developers contemplating better architectures—understand distributed systems and grow to the next level.

This course covers RPC communication techniques that maximize performance in large-scale MSA (Microservice Architecture) environments. Going beyond simple gRPC practice, you'll learn how to implement stable and efficient inter-service communication in real production environments where hundreds of microservices operate simultaneously. Based on Golang, the course covers Protocol Buffers (proto) syntax writing, automatic code generation and service implementation, gRPC structure and advantages over existing RPC, and performance optimization strategies with a practical focus. To ensure easy understanding for non-majors and server development beginners, the course provides step-by-step explanations from RPC concepts to gRPC's internal operating principles, enabling you to develop practical skills that can be immediately applied to real services.

This course is a master class that systematically covers the fundamental principles and practical applications of MongoDB. Starting with core MongoDB concepts, you will systematically learn essential topics for practical work, such as database design, CRUD operations, indexing, aggregation pipelines, performance optimization, transactions, and security. It explains topics step-by-step so even beginners can understand, and you can deeply learn the working principles of MongoDB through exercises and examples. This is the best introductory and practical course for developers who want to build strong MongoDB skills for practical work.

This course is a master class that teaches Kotlin's 🌺 Coroutine, covering everything from theoretical foundations to practical application in a standard manner. It systematically covers core principles and structure, the necessity of asynchronous programming, Coroutine builders and scopes, exception handling, channels, Flow, and other key features frequently used in practice, step by step. Each concept is explained with hands-on examples, making it easy for beginners to understand and immediately apply them. This is the best introductory and practical course for developers who want to build strong Coroutine skills for real-world use.

Let's build a project using Ktor, the most popular project in Kotlin, and master Kotlin! 😆

LeetCode explained by Dalle, a Korean developer working at a Silicon Valley startup! This is a practical LeetCode problem-solving course that doesn't just provide answer codes, but compares multiple approaches for each problem, analyzes time and space complexity together, and explains why certain solutions are more efficient. First, we write the most intuitive approach and analyze its time/space complexity to identify bottlenecks and improvement points. Then, we explore alternative approaches applying various data structures and algorithmic techniques, comparing the performance differences and pros and cons of each method. Through this, it helps you develop problem-solving skills to design efficient solution strategies on your own when facing new problems.

A course that helps you understand core data structure concepts and practice explaining them verbally in interviews

Listening to the interview speech can help you pass the interview with flying colors.

Pass rate 1% -> 66%, 2nd year salary achieved 6,000 ☑️ I've compiled all the know-how that transformed a resume that was rejected over 300 times into one that 'always passes' into a single book. Do you feel like you're falling behind even though you're working as hard as everyone else? If you're having trouble even passing document screening despite taking countless courses and building your specs, there's a high chance you're misunderstanding the 'rules of the game.' This book will teach you the 'rules of the winning game' itself, so that your efforts lead to the results you deserve.

This course is a practical design lecture that organizes the logic of passing interviews based on actual evaluation criteria used by public institution interviewers, tailored to each career stage of applicants. For early-career applicants, it presents stability and growth potential rather than perfection, For experienced professionals, it provides a performance structure translated into organizational language rather than a mere list of experiences, For career changers, it offers answers to organizational concerns rather than explanations of reasons. It clearly identifies why evaluation points differ by stage even for the same question, and what reassures or concerns interviewers. The focus is on redesigning passing answers not as "techniques for speaking well" but as structures that eliminate the possibility of rejection. This is a career stage-specific passing design guide that directly reflects the decision-making flow of interviewers, enabling early-career, experienced, and transitioning applicants alike to establish strategies suited to their position.

Master Algorithm Problem Solving with 100 Essential Silver Level Problems from Baekjoon Online Judge

For those who have chosen a career in information security/information technology and are preparing to move to large corporations/financial institutions, we will reveal our strategy for passing the exam. A current CISO who has personally recruited and recommended numerous people will share his secrets for passing the exam. He has heard from his acquaintances, security company CEOs and executives of large companies, and compiled a recruitment bible by collecting a vast amount of recruitment secret data.

This [Practical Employment] lecture covers only the most practical content. It comprises a lecture + e-book (total 144 pages). 1. This course strategically teaches the entire practical job search process, from interpreting job postings to resumes, cover letters, and interviews. 2. Students will learn to structure and articulate their experiences, and acquire tailored strategies and writing skills for each recruitment stage. 3. Ultimately, you can define your own career direction and complete actionable employment strategies.

We'll tell you what to do and what not to do when you have to give a technical/business presentation.

A course that helps you understand core database concepts and practice explaining them verbally in interviews

Through this lecture, students will be able to learn the basic and post-processing technology flow of semiconductors, and will be able to learn the content necessary to prepare for interviews at post-processing semiconductor companies.

Are you a non-major who doesn't know how to start learning C language? Did you learn C language as a major in school, but still can't write code? What's the point of studying C language for a long time? When you can't even create a single line of code properly... I'll pass on the know-how so you can program yourself. In this course, together with an experienced senior developer, you'll gradually learn C language grammar and application methods, and I'll guide you to a level where you can work on simple projects.

This course is for job seekers and career-changing backend developers preparing for coding tests with JAVA. We clearly identify question types by analyzing 195 actual past exam questions.

Strengthen your coding skills through coding test problems by learning Python-based data structures and algorithms!

A course that helps you understand core Java and Object-Oriented Programming (OOP) concepts, and includes practice explaining them verbally in interviews

Based on problems from major game companies like Nexon, NC, Krafton, and Netmarble, this explains essential C++ concepts and problem-solving skills that job seekers and career changers must know. Pass technical tests and interviews in one go with 10 years of actual exam questions.

Do you want to be good at speaking? Do you keep getting nervous when you present? Learn speech systematically from Heung Button, a 13-year announcer. Your life will change.

DevOps Interview Preparation: Master your interview preparation for Git, Docker, CI/CD, Terraform, Ansible, Kubernetes, and Monitoring.

A course that helps you understand core computer architecture concepts and practice explaining them verbally in interviews

This course explores the essential RPG game feature of "pathfinding" while naturally teaching data structures and algorithms. It quickly covers common technical interview questions, allowing you to prepare for coding interviews in a short period.